Dr. Gardoma said sharply, "Do you intend to go alone?"

"Why not?" interposed Urteil. "The heroics are cheap enough. Of course they'll go alone. There's nothing and nobody there, and they know it."

"Care to join us?" asked Bigman. "If you leave your big mouth behind you can fit into a suit."

"You wouldn't crowd one even with yours," snarled Urteil.

Dr. Gardoma said again, "There's no point in going alone if... "

"A preliminary investigation," said Lucky, "will do no harm. Actually, Urteil may be right. There may be no one there. At the worst, we'll keep in touch with you at the Dome and hope that we can handle any Sirians we meet. Bigman and I are used to handling tight situations."

"Besides which," added Bigman, his gnomish face puckering into a grin, "Lucky and I like tight situations."

Lucky smiled and rose to his feet. "If we may be excused... "

Urteil at once rose, turned, and stamped away. Lucky's eyes followed him thoughtfully.

Lucky stopped Hartley Cook as the latter passed Mm. He touched his elbow gently.

Cook looked up, his eyes all concern. "Yes. What is it, sir?"

Lucky said quietly, "May I see you in our quarters as soon as possible?"

"I'll be there in fifteen minutes. Is that all right?"

"Fine."

Cook was very little later than that. He stepped into their quarters softly, wearing the look of concern that seemed a constant part of him. He was a man in his late forties with an angular face and light brown hair that was beginning to be touched with gray.

Lucky said, "I had forgotten to tell you where our quarters were. I'm sorry."

Cook looked surprised. "I knew where you were assigned,"

"Well, good. Thank you for coming at our request."

"Oh," Cook paused. Then he said hurriedly, "Glad to. Glad to."

Lucky said, "There's a small matter of the insulation suits in this room. The ones intended for use on the Sun-side."

"The inso-suits? We didn't forget the instruction film, did we?"

"No, no. I viewed that. It's quite another thing."

Cook said, "Something wrong?"

"Something wrong?" crowed Bigman. "Look for yourself." He spread the arms in order to display the slashes.

Cook looked blank, then flushed slowly and grew round-eyed with horror. "I don't see... It's impos sible... Here at the Dome!"

Lucky said, "The main thing is to get it replaced."

"But who would do such a thing? We must find out."

"No use disturbing Dr. Peverale."

"No, no," said Cook, at once, as though he had not thought of it before.

"We'll find out the details in due time. Meanwhile I would like to get it replaced."

"Certainly. I'll attend to it promptly. No wonder you wanted to see me. Great Space-- -" He got to his feet in a kind of speechlessness and made as though to go.

But Lucky stopped him. "Wait, this is a minor thing. There are other things we must discuss. By the way, before we get to that-I take it you did not agree with Dr. Peverale's views on the Sirians."

Cook frowned. "I'd rather not discuss that."

"I watched you as he was speaking. You disapproved, I think."

Cook seat down again. His bony fingers clutched one another in a tight clasp and he said, "He's an old man. He's been all mixed up about the Sirians for years. Psychopathic, almost. He sees them under his bed. He blames them for everything. If our plates are overexposed, he blames them. Since he's been back from Skius he's worse than ever, because of what he claims he went through."

"What was it he went through?"

"Nothing terrible, I suppose. But they quarantined him. They assigned him a separate building. They were too polite sometimes. They were too rude other times. There was no way of suiting him, I suppose. Then they forced a positronic robot on him to take care of personal services."

"Did he object to that too?"

"He claims it was because they wouldn't come near him themselves. That's what I mean. He took everything as an insult."

"Were you with him?"

Cook shook his head. "Sirius would only accept one man, and he's senior. I ought to have gone. He's too old, really-too old."

Cook was talking in a brooding sort of way. He looked up suddenly. "This is all confidential, by the way."

"Completely," Lucky assured him.

"What about your friend?" said Cook uncertainly. "I mean, I know he's honorable, but he's a little, uh, hotheaded."

"Hey," began Bigman, stiffening.

Lucky's affectionate hand came down on the little fellow's head and brushed his hair down on his forehead. "He's hotheaded, all right," he said, "as you saw at the banquet table. I can't always stop him in time and sometimes, when he's riled, he uses his tongue and his fist instead of his head. That's something I always have to keep in mind. Still, when I ask him specifically to keep quiet about something, he is quiet, and that's all there is to it."

"Thank you," said Cook.

Lucky went on. "To get back to my original question: Do you agree with Dr. Peverale concerning the Sirians in this present case?"

"I don't. How would they know about Project Light, and why should they care? I don't see them sending ships and men and risking trouble with the Solar System just so they can break a few cables. Of course, I tell you this, Dr. Peverale has been feeling hurt for quite a while now... "

"In what way?"

"Well, Mindes and his group were established here while he was at Sirius. He came back and found them here. He knew they were coming eventually. It's been planned for years. Still, coming back and actually finding them here was a shock."

"Has he tried to get rid of Mindes?"

"Oh no, nothing like that. He's even been friendly. It's just that it makes him feel that someday he'll be replaced altogether, maybe someday soon, and I suppose he hates the thought. So it's pleasant for him to take charge and start a big affair about Sirians. That's his baby, you see."

Lucky nodded, then said, "Tell me, have you ever been on Ceres?"

Cook looked surprised at the change in subject but said, "Occasionally. Why?"

"With Dr. Peverale? Alone?"

"With him, usually. He goes more frequently than I do."

Lucky grinned. "Were you there at the time the pirates made their raid on Ceres last year?"

Cook smiled too. "No, but the old man was. We've heard the story several times. He was very angry about it. He's practically never sick, and this one time he was just completely out. He missed everything."

"Well, that's the way it goes... And, now, I think we'd better get to the main business. I didn't like to bother Dr. Peverale. As you say, he's an old man.

You're his second and quite a bit younger... "

Lucky smiled.

"Yes, of course. What can I do?"

"It's about the mines. I assume that somewhere at the Dome there are records, maps, charts, something which will tell us the arrangements of the main shafts and so on. Obviously, we can't wander at random."

"I'm sure there are," agreed Cook.

"And you can get them and perhaps go over them with us?"

"Yes, of course."

"Now as far as you know, Dr. Cook, the mines are in good shape, I hope. I mean, there's no danger of collapse or anything like that?"

"Oh no, I'm sure there's nothing of the sort possible. We're built right over some of the shafts, and we had to look into the engineering when the Observatory was first being set up. The shafts are well-buttressed and completely safe, particularly in Mercury's gravity."

"How come," asked Bigman, "the mines were shut down, if they're in such good shape?"

"A good question," said Cook, and a small smile broke through his expression of settled melancholy. "Do you want the true explanation or the interesting one?"

"Both," said Bigman at once.

Cook offered smokes to the others which were refused, then lit a cigarette after tamping it on the back of one hand in an abstracted manner. "The truth is this. Mercury is quite dense, and there were hopes that it would be a rich source of the heavy metals: lead, silver, mercury, platinum. It was, too; not as rich as might be, perhaps, but rich enough. Unfortunately, it was uneconomic. Supporting the mines here and transporting the ore back to Earth or even the Moon for processing raised the price too high.

"As for the interesting explanation, that's another thing completely. When the Observatory was first set up fifty years ago, the mines were still a going concern, though they were already closing down some of the shafts. The original astronomers heard stories from the miners and passed it on to the newcomers. It's part of the Mercurian legendry."

"What are the stories?" asked Bigman.

"It seems miners died in the shafts."

"Sands of Mars!" cried Bigman testily. "They die anywhere. You think anybody lives forever?"

"These were frozen to death."

"So?"

"It was a mysterious free/ing. The shafts were fairly well heated in those days, and their suit power units were in operation. The stories accumulate embroidery, you know, and, eventually miners wouldn't go into the main shafts in anything but gangs, wouldn't go into the side shafts at all, and the mines shut down."

Lucky nodded. He said, "You'll get the plans for the mines?"

"Right off. And replacements for that inso-suit too."

Preparations proceeded as though for a major expedition. A new inso-suit, replacing the one that had been slashed, was brought and tested, then laid to one side. After all, it would be ordinary space-suits for the dark-side.

The charts were brought and studied. Together with Cook, Lucky sketched out a possible route of exploration, following the main shafts.

Lucky left Bigman to take care of packing the adjunct-units with homogenized food and with water (which could be swallowed while still in the suit), make sure of the charge of the power units and the pressure on the oxygen tanks, inspect the working efficiency of the waste disposal unit and the moisture recirculator.

He himself made a short trip to their ship, the Shooting Starr. He made the trip via the surface, carrying a field pack, the contents of which he did not discuss with Bigman. He returned without it but carrying two small objects that looked like thick belt buckles, slightly curved, in dull-steel finish and centered by a rectangle in glassy red.

"What's that?" asked Bigman.

"Microergometers," said Lucky. "Experimental. You know, like the ergometers on board ship except that those are bolted to the floor."

"What can these things detect?"

"Nothing at a couple of hundred thousand miles like a ship's ergometer, but it can detect atomic power sources at ten miles, maybe. Look, Bigman, you activate it here. See?"

Lucky's thumbnail exerted pressure against a small slit in one side of the mechanism. A sliver of metal moved in, then out, and instantly the red patch on the surface glowed brightly. Lucky turned the small ergometer in this direction and that. In one particular position, the red patch glowed with the energy of a nova.

"That," said Lucky, "is probably the direction of the Dome's power plant. We can adjust the mechanism to zero that out. It's a little tricky." He worked painstakingly on the adjustment of two small controls so smoothly inset as nearly to be invisible.

He smiled as he worked, his engagingly youthful face lighting with pleasure. "You know, Bigman, there isn't a time I visit Uncle Hector but that he doesn't load me up with the Council's latest gadgets. He claims that with the chances you and I are always taking (you know the way he talks) we need them. Sometimes, though, I think he just wants us to act as field-testers for the gadgets. This one, though, may be useful."

"How, Lucky?"

"For one thing, Bigman, if there are Sirians in the mines, they'll have a small atomic power plant. They'll have to. They'll need power for heat, for electrolyzing water, and so on. This ergometer should detect that at ample distance. And for another thing-- "

He fell silent, and Bigman's lips compressed in chagrin. He knew what that silence meant. Lucky had thoughts which later he would claim had been too vague to talk about

"Is one of the ergometers for me?" he asked.

"You bet," said Lucky, tossing one of the ergometers toward him. Bigman snatched it out of the air.

Hanley Cook was waiting for them when they stepped out of their quarters, wearing their suits but with headpieces tucked under their arms.

He said, "I thought I'd lead you as far as the nearest entrance to the shafts."

"Thank you," said Lucky.

It was the tail end of the sleeping period in the Dome. Human beings always established an Earth-like alternation of waking and sleeping, even where there was no day and night to guide them. Lucky had chosen this time on purpose, since he did not want to enter the mines at the head of a curious procession. In this Dr. Peverale had co-operated.

The corridors of the Dome were empty. The lighting was dimmed. And as they walked, a heavy silence seemed to fall about them while the clank of their footsteps sounded even louder.

Cook stopped. "This is Entry Two."

Lucky nodded. "All right. I hope we'll be seeing one another again soon."

"Right."

Cook operated the lock with his usual gloomy gravity, while Lucky and Bigman put on their headpieces, clamping them firmly along the paramagnetic seams. Lucky took his first breath of canned air with what was almost pleasure, he was so accustomed to it.

Lucky first, then Bigman, stepped into the air lock. The wall closed behind them.

Lucky said, "Ready, Bigman?"

"You bet, Lucky." His words rang in Lucky's radio receiver, and his small form was a shadow in the extremely dim light of the lock.

Then the opposing wall opened. They could feel the puff of air escaping into vacuum, and they stepped forward through the opening once again.

A touch at the outer controls and the wall closed behind them again. This time, light was shut off altogether.

Standing in absolute darkness, they found themselves inside the silent and empty mines of Mercury.